1. (Field of the Invention)
The present invention relates generally to a load cell for electrically detecting a load imposed on a strain inducing element of a specific configuration, by the utilization of an electric characteristic of a strain detecting element such as, for example, a strain gauge, mounted on the strain inducing element, and a weighing apparatus such as an electronic scale using the load cell.
2. (Description of the Prior Art)
The load cell used in an electronic scale generally is employed in the form of a strain inducing element as shown in FIG. 12 and comprises fixed and movable rigid bodies a1 and a2 opposite to each other and a pair of parallel beams b1 and b2 extending between the fixed and movable rigid bodies a1 and a2. All of those elements a1, a2, b1 and b2 are defined by forming a cave c in a generally rectangular cubic metal block so that the fixed and movable rigid bodies a1 and a2 occupy respective opposite end portions of the metal block while the parallel beams b1 and b2 occupy respective opposite side portions of the metal block. The cave c is so shaped and so configured as to leave pairs of thin walled strain generating areas d1 and d2, d3 and d4, the strain generating areas d1 and d2 of one pair being defined at respective junctions of opposite ends of the beam b1 with the fixed and movable rigid bodies a1 and a2 while the strain generating areas d3 and d4 of the other pair are defined at respective junctions of opposite ends of the beam b2 with the fixed and movable rigid bodies a1 and a2.
The prior art strain inducing element A is so designed and so structured that, when a load W is applied to the movable rigid body a2, a considerable deformation occurs at the thin-walled strain generating areas d1 to d4 as shown by the phantom line, causing the movable rigid body a2 to undergo a parallel downward motion relative to the fixed rigid body a1. In other words, the strain generating areas d1 to d4 generate respective strains in a quantity proportional to the applied load W to reduce any possible adverse influence brought about by a bending moment. In practice, the fixed rigid body a1 of the strain inducing element A is rigidly secured to a base E of the electronic scale while the movable rigid body a2 is coupled with a scale table F. Strain detecting elements G such as, for example, strain gauges, are immovably placed on respective surfaces of the strain reducing element A in alignment with at least two of the strain generating areas d1 and d2 (or d3 and d4) so that a tensile strain and a compressive strain induced in the strain generating areas d1 and d2 as a function of the load placed on the scale table F can be detected by the respective strain detecting elements G thereby to provide an indication of the load W.
It has, however, been found that, even with the prior art measuring method discussed above, the strain generating areas d1 to d4 are not completely lessened from the adverse influence brought about by the bending moment of the strain inducing element on the strains induced therein, and it has been well recognized to minimize the adverse influence brought about by the bending moment in order to accomplish a more accurate load measurement.